Low-temperature detecting n-butanol sensing material and preparation method thereof

Abstract

The application discloses a kind of low-temperature detection n-butanol sensing material and preparation method thereof, belong to semiconductor metal oxide gas sensor technical field.Using solvothermal method, with a certain ratio of Ni source and W source as reactant, prepared Ni-doped W 18 O 49 Nanomaterial, the nanomaterial is by a large number of nanowires Composition 0.2~1.0 μm diameter red hair Dan-like microspheres, nanowire diameter is 5~15 nm, large specific surface area. It is prepared into gas sensitive element, and the best operating temperature is 160 o C, and the response value reaches 182.4 to 50 ppm n-butanol. Selectivity test is made to six common volatile organic compounds, and it is found that the sensing material has excellent selectivity to n-butanol. The sensing material prepared by the application has high response, good stability and good selectivity to n-butanol, and has good practical application value.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor metal oxide gas sensor technology, specifically involving the preparation of an element-doped tungsten oxide nanomaterial using a solvothermal method. The gas sensor assembled from this nanomaterial has excellent sensing performance for detecting n-butanol at low temperatures. Background Technology

[0002] Gas sensors made of semiconductor metal oxides have unique advantages such as ease of operation, real-time monitoring, and low cost, making them the preferred choice for detecting toxic and harmful gases. n-Butanol is a common volatile organic compound and a highly flammable liquid with a strong odor, widely used as a solvent. Therefore, monitoring n-butanol is crucial for safety and health. Currently, there are many reports on gas sensors for detecting n-butanol. The invention patent "n-butanol sensor based on CuO / S-SnO2 sensitive material and its preparation method and application" (CN115626657A) describes a CuO / S-SnO2 n-butanol gas sensor prepared at a calcination temperature of 400℃, which shows a response value of 26 for 100 ppm n-butanol gas at 180℃. The patent "A preparation method of a liquid-phase synthesized n-butanol gas sensor" (CN115326888A) describes a simple one-step hydrothermal method to prepare Au-LaFeO3 composite material, which, after coating, yields a gas-sensitive element that responds to 100 ppm n-butanol gas at 225℃. The response value for ppm n-butanol gas is 115; the patent "n-butanol gas-sensitive material and preparation method, n-butanol gas-sensitive device and preparation method" (CN108609664A) mixes tin chloride aqueous solution and citric acid aqueous solution evenly, adds cobalt chloride aqueous solution, stirs magnetically evenly, adds appropriate alkali in two batches, performs hydrothermal reaction, and calcines to obtain hollow cubic CoSnO3 nanomaterial. The sensor assembled based on this material has a response value of 19.12 for 100 ppm n-butanol gas at 200℃; the patent "a n-butanol gas sensor based on mesoporous WO3 material supported by noble metal Au and its preparation method" (CN105891272A) uses the hard template method to prepare mesoporous WO3, and then prepares Au-supported mesoporous WO3 material by impregnation method. The sensor prepared based on this material has a sensitivity of 6.8 for 10 ppm n-butanol at 250℃. Although some progress has been made in the research of semiconductor metal oxide gas sensors, it is necessary to further improve the technical parameters such as sensitivity, selectivity and stability of n-butanol sensors.

[0003] Tungsten oxide is an n-type semiconductor. x WO in (non-stoichiometric) materials 2.72 (W) 18 O 49Containing more oxygen vacancies, it is more stable in air, which is highly beneficial to its gas-sensing performance. In practical applications, many gas sensors prepared from raw samples have poor gas-sensing performance. Element doping is one method to enhance the gas-sensing performance of gas sensors. For example, the patent "Cerium-doped tungsten oxide composite material and hydrogen sulfide sensor, and preparation method" (CN114280111A) adds anhydrous cerium chloride dissolved in anhydrous ethanol to WCl6 dissolved in acetylacetone, stirs to obtain a dark green mixed solution, then adds a dry amphiphilic block copolymer dissolved in tetrahydrofuran, stirs, dries and cures, and then calcines to obtain cerium ion-doped mesoporous crystalline tungsten oxide material. The sensor prepared using this material exhibits a response value as high as 150 to 50 ppm hydrogen sulfide gas at 150℃, but its preparation method is relatively complex. Patent "Preparation of Nickel-Doped Tungsten Oxide and Its Gas Sensing Application" (CN116002757A) describes dissolving sodium tungstate dihydrate in deionized water, adding nickel chloride after continuous stirring, and performing a hydrothermal reaction at 180℃ for 8 h. The resulting material is then centrifuged, washed, dried, and calcined to obtain sheet-like nickel-doped tungsten oxide material. Gas-sensitive elements prepared based on this material show good response to acetone. Patent "Preparation Method of Nickel Cobalt Oxide / Tungsten Trioxide Nanocomposite Structure and Its Application in Gas-Sensitive Coatings, Elements, and Sensors" (CN113237926B) describes hydrothermally calcining nickel source, cobalt source, and urea with deionized water, then adding the obtained sample, tungstic acid, and lactic acid to deionized water, adjusting the pH with hydrochloric acid, and performing hydrothermal calcination again to obtain NiCo2O4 nanoflower-modified WO3 nanoplates. The sensor based on the composite material showed a response value of 116.9 for 20 ppm NO2 at 150℃. Currently, there are few reports or patents finding that tungsten oxide-doped materials respond to n-butanol, and there are no reports of M (nickel, cobalt, iron) element-doped tungsten oxide being used as a sensing material for detecting n-butanol. This invention obtained element-doped W through a one-step solvothermal method. 18 O 49 The method for preparing nanostructured powders is simple and convenient. Gas sensors prepared using this material exhibit high response and good selectivity to n-butanol. Summary of the Invention

[0004] This invention provides a simple method for preparing n-butanol sensing materials, which synthesizes element-doped W through a one-step solvothermal method and calcination. 18 O 49 Nanomaterials, sensors made from these materials exhibit excellent gas-sensing properties for n-butanol, with significant improvements in sensitivity and selectivity.

[0005] The present invention describes a high-response element M-doped W 18 O 49The n-butanol sensor made of nanomaterials consists of a ceramic tube substrate with two parallel ring-shaped gold electrodes and four platinum wires on its outer surface, a nanomaterial-sensitive material coated on the outer surface of the ceramic tube, and a nickel-cadmium heating coil placed inside the ceramic tube. Figure 1 The preparation steps are as follows:

[0006] The doping element M mentioned above is Ni, Co, or Fe.

[0007] 1. A sensing material for low-temperature detection of n-butanol and its preparation method:

[0008] Weigh 2.5-5 mmol of WCl6 and an appropriate amount of M(NO3)2·6H2O and dissolve them in 60-80 mL of anhydrous ethanol. Stir magnetically for 20-40 min. The preferred conditions are: 3.5 mmol of WCl6, 0.175 mmol of M(NO3)2·6H2O, 70 mL of anhydrous ethanol, and magnetic stirring for 30 min.

[0009] The above sample was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 160-200℃ for 8-15 h. After the reaction was completed, the sample was cooled to room temperature. The product was washed 2-5 times by centrifugation with ethanol and then dried in a vacuum drying oven at 50-70℃. The preferred conditions were: solvothermal temperature of 200℃, reaction time of 10 h, cooling to room temperature, washing 3 times by centrifugation with ethanol, and then drying in a vacuum drying oven at 60℃.

[0010] Finally, the obtained blue powder was placed in a muffle furnace and calcined at 300-500℃ for 1-3 h to obtain M-doped W. 18 O 49 Nanopowder. Preferred conditions are: calcination temperature of 300℃ and calcination time of 2 h.

[0011] Fabrication methods of nanomaterial-based sensors:

[0012] The sensor involved in this invention adopts a side-heated structure. The specific process is as follows: 20-50 mg of prepared powder is mixed with 1-2 drops of terpineol and ground in an agate mortar in one direction for 20-40 minutes to form a uniform slurry. The slurry is then evenly coated onto the surface of a ceramic tube with a brush to form a thin sensing material coating. After welding onto a base, it is aged for 2-3 days to produce a side-heated sintered gas-sensitive element. Figure 1 As shown.

[0013] Sensing performance testing of gas-sensitive elements made of nanomaterials:

[0014] In gas-sensing testing, the WS-30A tester is used to evaluate the performance of various gas sensors. Examples include measuring the response of a gas-sensing element to 50 ppm n-butanol at different temperatures; the response of a gas-sensing element to different concentrations of n-butanol at its optimal operating temperature; and the response of a gas-sensing element to six organic gases at its optimal operating temperature.

[0015] Sensing mechanism of n-butanol gas sensor:

[0016] For n-type metal oxides, the gas-sensing principle mainly involves regulating the charge transfer and gas adsorption / desorption processes induced by the electron depletion layer. When nanomaterials are exposed to air, oxygen is adsorbed onto the material surface. Subsequently, oxygen molecules capture electrons from the material's conduction band, creating a loss layer on the surface and increasing resistance. Ion formation type (O2) - O - O 2- The adsorption rate depends on the operating temperature, as shown in equation (1-4). Therefore, when the operating temperature is 100~260℃, the adsorbed oxygen is mainly in the form of O2. - It exists in the form of.

[0017]

[0018] When the sensor is exposed to n-butanol, as shown in equations (5, 6), the reducing gas reacts with O2. - The (ads) reaction releases trapped electrons back into the material, increasing the number of electrons in the conduction band and forming a thin depletion layer that reduces the sensor's resistance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the gas-sensitive element in the embodiment.

[0020] Figure 2 (a) is a scanning electron microscope (SEM) image of the sample obtained in Example 4;

[0021] Figure 2 (b) is a transmission electron microscope (TEM) image of the sample obtained in Example 4;

[0022] Figure 3 The XRD patterns are of the samples obtained in Examples 1 and 4;

[0023] Figure 4 The preparation process of the sample obtained in Example 4 is as follows;

[0024] Figure 5 XPS images of the samples obtained in Examples 1 and 4;

[0025] Figure 6 The BET plot of the sample obtained in Example 4;

[0026] Figure 7 The graphs showing the response values ​​of the gas-sensitive elements prepared in Examples 1, 2, 3, 4, and 5 to 50 ppm n-butanol as a function of operating temperature.

[0027] Figure 8 The gas sensing performance of the gas sensing elements prepared in Examples 1 and 4 at the optimal operating temperature for different concentrations of n-butanol gas is shown in the test graph.

[0028] Figure 9 The graph shows the sensitivity performance of the gas-sensitive elements prepared in Examples 1 and 4 to different organic gases at the optimal operating temperature of 50 ppm. Detailed Implementation

[0029] The present invention will be specifically described below with reference to embodiments, enabling those skilled in the art to implement it after reading this specification. Embodiment 4 describes preferred preparation conditions. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0030] Example 1: Undoped W 18 O 49 Preparation of nanomaterials and fabrication of gas-sensitive elements based on these materials:

[0031] (1) Weigh 3.5 mmol WCl6 and dissolve it in 70 mL of anhydrous ethanol, and stir for 30 min;

[0032] (2) The above sample was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 200°C for 10 h.

[0033] (3) After the reaction was completed, the mixture was cooled to room temperature. After washing three times with ethanol by centrifugation, it was dried overnight in a vacuum drying oven at 60°C to obtain a blue powder.

[0034] (4) The obtained powder was placed in a muffle furnace and calcined at 300°C for 2 h to obtain the final product;

[0035] (5) Take 30 mg of the prepared powder and put it into an agate mortar. Add 1-2 drops of terpineol and grind in one direction for 30 min to form a slurry. Use a brush to take an appropriate amount of slurry and coat it on the outer surface of a commercially available ceramic tube. Let it stand for 2 days. First, weld the ceramic tube to the base, and then pass the heating wire through the ceramic tube and weld it to the base.

[0036] (6) The prepared sensor was aged under an aging table for 36 h to obtain W based on calcination at 300℃. 18 O 49 Gas-sensitive elements made of nanomaterials.

[0037] Example 2: 1 mol% Ni-doped W 18 O 49 Preparation of nanomaterials and fabrication of gas-sensitive elements based on these materials:

[0038] (1) Weigh 3.5 mmol WCl6 and 0.035 mmol Ni(NO3)2·6H2O and dissolve them in 70 mL of anhydrous ethanol, and stir for 30 min;

[0039] (2) The above sample was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 200°C for 10 h.

[0040] (3) After the reaction was complete, the mixture was cooled to room temperature. After washing three times with ethanol by centrifugation, it was dried overnight in a vacuum drying oven at 60°C to obtain a blue powder;

[0041] (4) The obtained powder was placed in a muffle furnace and calcined at 300°C for 2 h to obtain the final product;

[0042] (5) The gas-sensitive element was prepared using the same method as in Example 1, yielding W based on 1 mol% Ni doping. 18 O 49 Gas-sensitive elements made of nanomaterials.

[0043] Example 3: 3 mol% Ni-doped W 18 O 49 Preparation of nanomaterials and fabrication of gas-sensitive elements based on these materials:

[0044] (1) Weigh 3.5 mmol WCl6 and 0.105 mmol Ni(NO3)2·6H2O and dissolve them in 70 mL of anhydrous ethanol, and stir for 30 min;

[0045] (2) The above sample was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 200°C for 10 h.

[0046] (3) After the reaction was complete, the mixture was cooled to room temperature. After washing three times with ethanol by centrifugation, it was dried overnight in a vacuum drying oven at 60°C to obtain a blue powder;

[0047] (4) The obtained powder was placed in a muffle furnace and calcined at 300°C for 2 h to obtain the final product;

[0048] (5) The gas-sensitive element was prepared using the same method as in Example 1, yielding W based on 3 mol% Ni doping. 18 O 49 Gas-sensitive elements made of nanomaterials.

[0049] Example 4: 5 mol% Ni-doped W 18 O 49 The preparation of nanomaterials and the preparation of gas-sensitive elements based on these materials, this embodiment is a preferred example:

[0050] (1) Weigh 3.5 mmol WCl6 and 0.175 mmol Ni(NO3)2·6H2O and dissolve them in 70 mL of anhydrous ethanol, and stir for 30 min;

[0051] (2) The above sample was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 200°C for 10 h.

[0052] (3) After the reaction was complete, the mixture was cooled to room temperature. After washing three times with ethanol by centrifugation, it was dried overnight in a vacuum drying oven at 60°C to obtain a blue powder;

[0053] (4) The obtained powder was placed in a muffle furnace and calcined at 300°C for 2 h to obtain the final product. Figure 2 The sample appears to consist of numerous rambutan-shaped microspheres with diameters ranging from 0.2 to 1.0 μm, composed of nanowires with dimensions of 5 to 15 nm. Figure 3 In the XRD pattern, all diffraction peaks point well to the monoclinic structure W. 18 O 49 Clearly, the incorporation of Ni did not alter its monoclinic crystal structure.

[0054] (5) The gas-sensitive element was prepared using the same method as in Example 1, yielding W based on 5 mol% Ni doping. 18 O 49 The fabrication process of a gas-sensitive element made of nanomaterials is shown in the flowchart below. Figure 4 .

[0055] Example 5: 7 mol% Ni-doped W 18 O 49 Preparation of nanomaterials and fabrication of gas-sensitive elements based on these materials:

[0056] (1) Weigh 3.5 mmol WCl6 and 0.245 mmol Ni(NO3)2·6H2O and dissolve them in 70 mL of anhydrous ethanol, and stir for 30 min;

[0057] (2) The above sample was transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 200°C for 10 h.

[0058] (3) After the reaction was complete, the mixture was cooled to room temperature. After washing three times with ethanol by centrifugation, it was dried overnight in a vacuum drying oven at 60°C to obtain a blue powder;

[0059] (4) The obtained powder was placed in a muffle furnace and calcined at 300°C for 2 h to obtain the final product;

[0060] (5) The gas-sensitive element was prepared using the same method as in Example 1, yielding W based on 7 mol% Ni doping. 18 O 49 Gas-sensitive elements made of nanomaterials.

[0061] Example 6: W 18 O 49 Testing the sensing performance of gas-sensitive elements doped with nanomaterials

[0062] The characteristics of the gas-sensitive element were tested using the static gas mixing method. The WS-30A gas-sensitive element testing system was used to test the W doping concentration at different operating temperature ranges from 100℃ to 260℃ under a heating voltage of 5.0 V. 18 O 49 The response curve of the gas-sensitive element prepared from the material to 50 ppm n-butanol as a function of operating temperature is shown below. Figure 7 ,from Figure 7 It can be seen from this that the Ni doping concentration is 5 mol% W 18 O 49 The gas-sensitive element exhibits the highest response value to n-butanol, at an operating temperature of 160℃, which is 182.4. Figure 5 XPS analysis showed that W 18 O 49 The oxygen vacancy rate was 28.6% lower than that of 5 mol% Ni in W. 18 O 49 (40.0%) Figure 6 BET analysis showed that 5 mol% Ni in W 18 O 49 The larger specific surface area provides more adsorption active sites for reaction with n-butanol gas, resulting in a higher response value.

[0063] W without doping and doped with 5 mol% Ni 18 O 49 The test results of the gas-sensitive element at 160℃ for 10, 20, 50, 100, and 200 ppm n-butanol gas are as follows: Figure 8 As shown, the response of the gas-sensitive element to n-butanol increases with increasing gas concentration. 18 O 49 The response to 10–200 ppm n-butanol was lower than that to 5 mol% Ni at W. 18 O 49 (44.4, 78.4, 182.4, 342.9 and 640.9);

[0064] Similarly, using the static gas mixing method, the WS-30A gas-sensitive element testing system was used to test undoped and 5 mol% Ni-doped W gas at a heating voltage of 5.0 V. 18 O 49 The response of gas-sensitive elements made from materials to other organic compounds, such as Figure 9 W was shown to contain 5 mol% Ni. 18 O 49 The gas-sensitive element prepared from the material exhibited response values ​​of 1.7, 2.9, 182.4, 13.0, 1.5, and 1.8 at 160℃ to 50 ppm of ethanol, isopropanol, n-butanol, acetone, formaldehyde, and n-hexane, respectively. Figure 9 The test results show that W doped with 5 mol% Ni 18 O 49 The gas-sensitive element has good selectivity for n-butanol gas.

Claims

1. A high-response Ni-doped W 18 O 49 The n-butanol sensor is characterized by, The Ni-doped W 18 O 49 The preparation process includes the following steps: Step 1: Weigh 2.5 ~ 5 mmol WCl6 and an appropriate amount of Ni(NO3)2·6H2O and dissolve them in 60 ~ 80 mL of anhydrous ethanol, and stir magnetically for 20 ~ 40 min; the amount of Ni(NO3)2·6H2O is 0.175 mmol; Step 2: The sample is transferred to a stainless steel high-pressure reactor lined with polytetrafluoroethylene and reacted in an oven at 160~200℃ for 8~15 h. After the reaction is completed, the sample is cooled to room temperature. The product is washed 2~5 times by centrifugation with ethanol and then dried in a vacuum drying oven at 50~70℃. Step 3: Finally, the obtained blue powder is placed in a muffle furnace and calcined at 300~500℃ for 1~3 h to obtain Ni-doped W. 18 O 49 Nanopowder is the sensing material for detecting n-butanol.

2. A high-response Ni-doped W as described in claim 1 18 O 49 The n-butanol sensor is characterized by, The conditions described in step 1 are as follows: 3.5 mmol of WCl6, 70 mL of anhydrous ethanol, and 30 min of magnetic stirring.

3. A high-response Ni-doped W as described in claim 1 18 O 49 The n-butanol sensor is characterized by, The conditions described in step 2 are as follows: the solvothermal temperature is 200℃, the reaction is carried out for 10 h and then cooled to room temperature, washed three times by centrifugation with ethanol, and then dried in a vacuum drying oven at 60℃.

4. A high-response Ni-doped W as described in claim 1 18 O 49 The n-butanol sensor is characterized by, The conditions described in step 3 are: calcination temperature of 300℃ and calcination time of 2 h.

5. A high-response Ni-doped W as described in claim 1 18 O 49 The n-butanol sensor is characterized by, It consists of a ceramic tube substrate with two parallel ring-shaped gold electrodes and four platinum wires on the outer surface, a nano-sensitive material coated on the outer surface of the ceramic tube, and a nickel-cadmium heating coil placed inside the ceramic tube.

6. A high-response Ni-doped W as described in claim 1 18 O 49 The n-butanol sensor is characterized by, The sensor adopts a side-heated structure, and the specific process is as follows: 20-50 mg of the prepared sensing material is mixed with 1-2 drops of terpineol and ground in an agate mortar in one direction for 20-40 minutes to form a uniform slurry. The slurry is then evenly coated onto the surface of a ceramic tube with a brush to form a thin sensing material coating. After welding it onto the base, it is aged for 2-3 days to produce a side-heated sintered gas-sensitive element, which is the n-butanol sensor. The sensor has a response value of 182.4 for n-butanol at an operating temperature of 160℃, and has good selectivity.

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